Fix case when routes have both '/' and '*'

[chadrien]

• I added new tests for the issue I fixed or the feature I built
• I ran npm test for the package I'm modifying
• I used npm run commit instead of git commit

Closes #16 #30 #17 #18

I basically saw that #16 was existing (and I need a fix for it :)), that #17 and #18 already aimed to fix it but were never merged and are now behind master and conflicting as the typescript migration happened after them, so I simply took the changes from #18 but from an up-to-date master branch.

In order to have npm test to pass, I also had to make the same changes as in #30.

[siassaj]

@staltz any chance we can rerun travis CI and maybe integrate this in?

( I think travis CI's node machine at the time shit itself on const in strict mode)

[staltz]

I don't have time to maintain switch-path. Does someone want to fork it and maintain?